In this Oct. 25, 2013 photo, petroleum coke, or petcoke, is stored on barges on the Calumet River near the Chicago Skyway Bridge in Chicago. The grainy black byproduct of oil refining has been piling up along Midwest shipping channels and sparking a new wave of environmental concerns. The volume and size of petcoke piles has grown sharply, especially in the Midwest.

Two environmental groups on Monday sent a letter to billionaire brothers Charles and David Koch, saying they intend to file a lawsuit against them for polluting a primarily low-income area of Chicago with thick, black, oily dust.

The letter sent by the Southeast Environmental Task Force (SETF) and Natural Resources Defense Council (NRDC) gave official 90-day notice of intent to sue the Koch brothers and 10 of their companies, including the KCBX Terminals Company, in federal court. The lawsuit will seek to hold them liable for the harmful effects of pollution caused by coal and petroleum coke, or petcoke — a dusty byproduct of tar sands oil refining — which their companies allegedly help store in large piles along the Calumet river on Chicago’s southeast side.

Because petcoke can be used as fuel, KCBX buys it from the Detroit Marathon Oil Refinery and stores it in piles by the river until it can be shipped and sold on the international market. When the wind blows, though, the dusty petcoke blows from the piles into the air, settling onto people’s homes and into the river.

The resulting soot has harmed human health, the environment, and overall quality of life, the groups’ letter said.

“Koch’s neighbors have kept the windows and doors of their homes closed in an effort to limit their exposure to dust, only to discover that some still finds its way inside,” the letter said, sparing little detail into the lives of those who reside near the piles:

“They have tasted dust in their mouths and seen dust settle on their skin and discolor their clothes. …. They have been unable to gather for barbeques and outdoor markets without having black dust fall on their faces and clothes and contaminate their food. They have been forced to suspend outdoor games by storms that fill the air with swirling black dust. They have worried about letting children play outside. They have smelled foul odors that leave them feeling nauseous and exhausted. They have struggled to breathe.

This noxious pollution is part of daily life for Koch’s neighbors. It worsens each time the wind blows.”

A representative for Koch Industries did not immediately return ThinkProgress’ request for a response to the allegations.

It will likely be difficult to hold the Koch brothers individually responsible for the alleged actions of their large companies. Suing company officers requires a legal maneuver called “piercing the corporate veil,” a tactic used in “exceptional situations” when it can be proven that the officers themselves were the main drivers of the alleged violation. Because a large corporation like Koch Industries has many levels of decision-making, it won’t be easy to prove in court that the brothers were at the helm of each one.

Still, a spokesperson from the NRDC confirmed that its attorneys intend to pursue individual counts against the brothers. Indeed, the Chicago piles of petcoke have become so entangled in the business empire of the Koch brothers that they have earned the nickname “PetKoch.”

Despite months of complaints, however, Illinois officials have denied there is a public health problem from swirls of black petrochemical dust blowing through the air. In January, the Illinois Pollution Control Board rejected state Gov. Pat Quinn’s proposed emergency rules to control the piles, saying there was no imminent threat to public health and safety from petcoke.

Opponents of the piles did score one slight win against the piles on Tuesday, when the city council’s zoning committee passed an ordinance banning new petcoke facilities from opening in the city, and prevent existing sites from expanding.

Many opponents of petcoke still decried the passage, though, saying it fell short of what they had really wanted.

“We asked to ban petcoke,” Fred Sosinski, a Chicago resident, told ProgressIllinois. “This ordinance in insulting to the people of the Southeast side.”

As petcoke is a byproduct of refining tar sands oil, its presence in the United States stands to increase if the controversial Keystone XL pipeline is approved. If approved, the pipeline would bring tar sands oil from northern Canada down to refineries in Texas and Louisiana, where the byproduct would also likely be stored and shipped overseas.